The conventional water treatment has employed a method for collecting sewage in cleaning equipment or a sewage treatment plant for treating sewage. However, household miscellaneous wastewater contributes largely to pollution. Household miscellaneous waste water contains various substances. Among them, there is concern that detergents could provide an adverse affect on the ecological system. In particular, various surfactants contained in synthetic detergents remarkably harm the existence of bacteria and protozoa used as a main body in a sewage treatment technique, which lowers the treatment capacity and leads a vicious circle of increase in pollution. Moreover, in a final process of sewage treatment, many chlorine-type bactericides are used, thus the influence on the ecological system becomes serious.
Considering that the household miscellaneous waste water including surfactants lowers the treatment capacity of the sewage treatment plant and chlorine-type bactericides are being used, it can be said that an intermediate treatment process in the sewage treatment plant would not be sufficient as a basic solution.
Recently, the accumulation of the above problems causes serious pollution of rivers and oceans, and recovery has been tried at an expensive cost. However, these problems remain unsolved, and become more serious. In such situations, people's attention has been drawn to soap that is decomposed by natural microorganisms, and a public movement to use soap made from waste oil has been growing. However, when soap has a low saponification degree and an insufficient cleaning power, it is apparent that water quality is deteriorated in accordance with the increase of soap usage.
Patent reference 1: Japanese Unexamined Patent Publication 2002-226893
Patent reference 2: Japanese Unexamined Patent Publication 2002-128683